The present invention relates, in general, to an apparatus for measuring a tensile force.
It is generally known to use such an apparatus, also called "force gage", to measure a tensile force for use in a pneumatic device. Conventional force gages typically include a pair of longitudinal arms in spaced-apart parallel disposition, and a pair of transverse arms in spaced-apart parallel disposition and hingedly interconnecting the longitudinal arms. One of the longitudinal arms is acted upon by a tensile force and moved thereby in the direction of the tensile force, whereby both longitudinal arms are oriented in a direction parallel to the tensile force. The other longitudinal arm is secured at its upper end, for example, to a traction means. A probe is positioned between the transverse arms and has a casing securely fixed to one of the longitudinal arms for generating a pneumatic pressure signal commensurate with the tensile force. Projecting out of the casing of the probe is a pressure bolt which is acted upon in dependence on the tensile force by a transverse arm which is securely fixed to the downwardly moving longitudinal arm.
The pneumatic lifting device may, for example, be a hoist or a control mechanism for tensile stress in a take-up reel. Examples of probes include a bulk modulus or a precision pressure controller.
As a consequence of their design, conventional force gages of this type can be loaded only to a certain limit value and thus yield a limit control pressure that is proportional to the limit value. For this reason, the practical use of conventional force gages is very narrow so that hoist manufacturers are forced to store an array of different force gages to satisfy varying load-carrying capabilities of hoists.